Preparation of olefinic compounds



Patented Apr. 18-, 195i!v UNITED STATES PATENT OFFICE 2.504.010 $1? Sifilfifiiffi? 1311.

to E. I. du Pont de Nemours & Company. Wilmington, M, a corporation of Delaware No Drawings.

This inventionrelates to the preparation of olefinic compounds and particularly certain halooleflnic compounds such as the sym. dichlorethylenes and vinyl chloride.

"Halooleilnes such as the cis and trans dichlorethylenes have been prepared previously by the fvapor phase'reaction of hydrogen with polyhalo- ,is concerned with an improved method of preparing cis and trans dichlorethylenes, and other 'olefinic compounds, such as unsym. dichlorethylone, vinyl chloride and the like.

- It is an object of my invention to provide an ,=improved method for preparing oleflnic hydrocarbons and halooleflnic hydrocarbons containing 2 to 3 carbon atoms. A further object is to provide an improved catalytic hydrogenation m thod forpreparing such compounds, particu-. larly halogenated olefines, such as the halogenated ethylenes, from saturated polyhalogenated hydrocarbons of 2 to 3 carbon atoms, particularly the poly halogenated ethanes. A specific object is to provide an improved method of preparing the cis and trans isomers of dichlorethylene and vinyl chloride from sym. tetrachlorethane and 1,2,2-trichlorethane, respectively, by vapor phase reactions with hydrogen in the presence of im-.

gproved catalysts; Still further objects will be apparent from the ensuing description.

The above objects are accomplished in accordance with the present invention by reacting hydrogen in the vapor phase at an elevated temperature in the presence of a metallic copper or iron catalyst with an iodine-free, saturated polyhalogenated hydrocarbon having from 2 to 3 carbon atoms and at least 1 chlorine or bromine atom attached to each of 2 adjacent carbon. atoms. The reaction may be carried out with good results at temperatures over a rather wide range, but a temperature of 350 to 425 is preferred. Lower temperatures, e. g., as low as Application June 18, 1946, eriai No. 077,517

18 Claims. (Cl- 260-654) sion at such lower temperatures is. poorer than at the preferred temperatures. At temperatures above about 500 C. undesirable side reactions and decomposition reactions occur at excessive rates.

the catalyst consists of about 10% by weight of freshly reduced copper or iron impregnated on a granular refractory material such as pumice, silica gel. alumina gel, porcelain or flrebrick. particularly the latter. Lower catalyst concentrations. e. g., as low as 5%. on such materials may also be used, but concentrations around 10% give best results. The catalyst may be prepared by well-known methods such as by impregnating a suitable porous support material with a copper or iron salt such as copper or iron nitrate or a copper or iron halide, followed by the reduction of the compound to the metallic state by hydrogenation at temperatures, for example, of around 400 to 500 C.

The use of a copper catalyst is preferred in most instances. when an iron catalyst is employed there is a tendency for a thermal cracking of the polyhalohydrocarbon reactant to occur along with the reaction between the polyhalohydrocarbon and hydrogen. The cracking reaction occurs to a greater extent when using iron as catalyst. However, iron does effectively catalyze the desired reaction and since products formed by the cracking reaction are useful products iron may be employed with good results. If. however, it is desired to obtain maximum yields of compounds such as the cis and trans dichlorethylenes, a copper catalyst will generally be used in preference to iron since copper is more effective and less cracking of the starting reactant occurs when copper is used.

The saturated polyhalohydrocarbons which are suitable for use as starting materials are iodinefree, saturated compounds containing 2 to 3 carbon atoms. The compounds have at least 1 chlorine or bromine atom attached to each of 2 adjacent carbon atoms, and when those are the only halogen atoms in the molecule. the result- 300 C., may be employed although the converins olefinic' compound will be a non-halogenated each of 2 adjacent carbon atoms.

olefin, i. e. ethylene or propylene. The preferred polyhalohydrocarbons are those which have at least 3 halogen atoms per molecule, which compounds will result in the formation of haloolefines. The compounds whose structural formula are listed below are illustrative of the compounds which may be used:

CHClzCHClCI-Ia CHzClCCl: CHzClCClaCHa CHzClCHCh CHClzCClzCI-Ia CClaCCla CClaCHClCH: CHClaCCl: CI-IzClCHClCHzCl CHzClCHaCl CHClzCHCl:

The polybromides corresponding to the above polychlorides may also be used as may also the following mixed halides:

CClsCClF: CHBrClCI-IBrCl CHClzCClF: cmsrcicnrca. CI-IzBrCBrClClh The pol'yhaloethanes, particularly sym. tetrachlorethane and 1.2.2-trichlorethane. are the preferred reactants from which haloethylenes and particularly cis and trans dichlorethylenes and vinyl chloride, are obtained as the chief products.

The type of reaction which takes place to yield the olefllnic compounds in accordance with the invention is believed to involve the reaction of 2 atoms of hydrogen with 2 halogen atoms of the polyhalohydrocarbon. each of which is a chlorine or bromine atom and l of which is positioned on There are formed 2 mols of hydrogen halide and an oleflnic hydrocarbon or halooleiinic hydrocarbon. in

which the 2 carbon atoms referred to above are finally joined by a double bond as illustrated by the following equations:

when the starting polyhalohydrocarbon contains 2 different halogen atoms on the 2 adjacent carbon atoms, the halogen of higher atomic weight is preferentially removed by the reaction with hydro en. Thus, in the case of sym. dichlordlbromethane, the bromine atoms are removed in preference to the chlorine atoms, to form 2 mols of hydrogen bromide and cis and trans dichlorethylenes as the haloethylene products.

The present method may be used efl'ectively to produce halooleflnes having at least 1 halogen atom other than iodine on at least 1 of 2 adjacent carbon atoms joined by a double bond, as in the case of the production of vinyl chloride or cis and trans dichlorethylene; or. the resulting product may contain a halogen other than iodine on a carbon atom other than those Joined by the double bond. as in the case of the production of allyl chloride from 1,2,3-trichlorpropane.

The invention is further illustrated by the following examples in which yield figures are based upon the amounts of the starting polyhalohydrocarbon not recovered as such, and conversion figures are based on the amounts fed.

Example 1 A reactor consisting of a mm; glass tube in. long was secured in a vertical position and provided at the top with two inlets and with a thermocouple well extending the' length of the reactor. The bottom end of the reactor was provided with an outlet passing to a cold water scrubber which functioned to dissolve out hydrogen halides from the product gases and condense out most of the product chlorohydrocarbons. The scrubber was connected to a low temperature cooler for condensing product not recovered in the scrubber. The reactor tube was surrounded by afurnace and the upper half of the tube was packed with $4 in. cubes of flrebrick and the lower half with similar cubes of firebrick which had .been impregnated with copper catalyst. Means were provided for delivering hydrogen and the halohydrocarbon to be reacted to the upper part of the reactor at uniform desired rates. The upper half of the packed tube functioned as a vaporizer and preheater whereas the bottom half served as the reactor proper.

The material packed into the bottom half of the tube was impregnated with sumcient copper chloride to give a catalyst body containing 10% by weight of copper after the'copper chloride had been reduced to the metallic state. After treating the firebrick cubes with the copper chloride solution, the mass was placed in the reactor tube and dried by a stream of air. Re-

duction was then accomplished by means of a in'the lower part of the reactor tube occupied a volume of 0.0389 cu. ft.

While maintaining a temperature of 370-390 C. in the vaporizing section of the glass tube and a temperature of 375385 in the part of the tube containing the catalyst, hydrogen and sym.

. tetrachlorethane were fed into the system at rates gen were fed.

of 0.0265 cu. ft. (STP) and 5.42 grams per minute, respectively. During 4 hours a total of 7.74 mols of tetrachlorethane and 8.04 mols of hydro- That amount of hydrogen corresponds to 104% of theoretical. 8.57 mols of hydrogen chloride were recovered from the product gases, together with a mixture of chlorohydrocarbons which upon fractionation yielded the following:

The run for this example was carried out using the same catalyst, equipment and procedure described for Example 1. During the course of 4 hours, 7.48 mols of sym. tetrachlorethane corresponding to 5.24 grams per minute and 7.04 mols of hydrogen corresponding to 0.0231 cu. ft. per minute were passed into the reactor. Both the vaporizer and catalyst sections of the reactor were maintained at a temperature of 430- 440' C. The hydrogen fed was 94% of the theoretical amount. .There were recovered 14.05 mols 'of hydrogen chloride along with a mixture of In a run similar to Example 1 there was employed 0.0389 cu. it. 01' a catalyst consisting of. V4 in. ilrebrick cubes impregnated with 10% by weight of freshly reduced iron. The preheater temperature was 330-840 C. and the reactor temperature 400-415 C. There were led at uniform rates during 4 hours 6.63 mols or sym. tetrachlorethane and 7.34 mols 01' hydrogen. There were recovered 6.55 mols of hydrogen chloride and a mixture of chlorohydrocarbons which on fractionation yielded:

Moi Per Product Mols Cen asa Conversion mu .dichlorethylene 0.041 0.0 as Trsrls t iichlorethylenc ll. 5 l4. 2 Oisdichlorethvlenc 14.5 17.8 'lrichloretliyiene 44.4 54.8 'letrschlorcthylenc 5. 3 s. 5 Te thanerecovcred .258 19.0

Totals. 6. 310 05. 3 94. l

trample 4 Vapors oi 1,2,2-trichlorethane, 9.77 mols, with 10.97 mols of hydrogen were passed during 6.25 hours over 0.011 cu. it. of a copper catalyst similar to that described in Example 1 at a temperature of 410-440 C. The products obtained and the conversions thereto were as follows:

Moi For Product Cent Conversion Vinyl chloride 40. Un'sym. dichloreth lene. 0.6 'lrsns dichlorethy no 2. 9 Cl: lilorethylenc 0. 5 Unrescted l,2,2-trichloretha 34. 6 High boiling products (about). 2.6

Satisfactory results may be obtained employing equimolar quantities of the reactant polyhalohydrocarbon and hydrogen. Either one of the reactants may be used in excess with good results, but as a general rule no particular advantage results from employing an excess of either reactant. In general, the process of the invention will be carried out at atmospheric pressure, but pressures above or below atmospheric pressure may be used ii desired.

It will be noted from the above examples that in general the amount of products, such as trichloi-ethylene. which are formed by thermal cracking of the starting halohydrocarbon increases as the temperature is increased. This is not particularly objectionable since trichlorethylene, for example. is itself a valuable product. However, when the object is to obtain as high a conversion as possible of compounds such as the dichlorethylenes or vinyl chloride, the higher temperatures in the operable temperature range,

e. g., temperatures above about 425' 0., should be avoided since at such higher temperatures the cracking reaction to produce, for example, trichlorethylene, occurs quite extensively, particulariy'when iron is employed as catalyst. Also, when operating at the higher temperatures there is a tendency for dehalogenation to proceed beyond, for example, the dichlorethylene stage when employing sym. tetrachlorethane as a reactant, with the result that products such as acetylene are formed which are relatively unstable'at high temperatures particularly in the presence of metals.

All of the halooleflne products which may be obtained when practicing the present invention, particularly the chloroethylenes, are useful for a variety of purposes. Thus, the dichlorethylenes, trichlorethylene, and tetrachlorethylene have valuable solvent properties and such products together with vinyl chloride are useful for the production of resins of various types.

I claim:

1. A process for producing an olefinic compound comprising reacting hydrogen at a temperature of 300 to 500 C. in the presence of a metallic catalyst from the group consisting of copper and iron, with the vapors of a saturated polychlorohydrocarbon having from 2 to 3 carbon atoms and at least one chlorine atom on each of two adjacent carbon atoms.

2. The process of claim 1, wherein the reaction is carried out at a temperature of 350 to 425 C.

3. A process for producing a chlorooleilnic compound comprising reacting hydrogen at a temperature 01200 to 500 C. in the presence of a metallic catalyst from the group consisting of copper and iron, with the vapors of a saturated polychlorohydrocarbon having from 2 to 3 carbon atoms and at least 3 chlorine atoms with at least 1 chlorine atom on each of two adjacent carbon atoms.

4. The process oi claim 3, wherein the reaction is carried out at a temperature of 350 to 425 C.

5. The process 01 claim 3, wherein the reactants" are employed in approximately molar proportions.

6. The process of claim 3, wherein the polychlorohydrocarhon contains 2 carbon atoms.

'1. The process of claim 3, wherein the polychlorohydrocarbon employed is symmetrical tetrachlorethane.

8. The process or claim 3, wherein the polychlorohydrocarbon employed is 1,2,2-trichlorethane.

9. A process for producing an oleflnic compound comprising reacting hydrogen at a temperature of' 300 to 500 C. in the presence of a metallic copper catalyst, with the vapors of a saturated polychlorohydrocarbon having from 2 to 3 carbon atoms and at least one chlorine atom on each of two adjacent carbon atoms.

10. A process for the production of a chlorooleflnic compound comprising reacting hydrogen at a temperature of 300 to 500 C. in the presence of a metallic copper catalyst, with the vapors oi a saturated polychlorohydrocarbon having from 2 to 3 carbon atoms and at least 3 chlorine atoms with at least one chlorine atom on each of two adjacent carbon atoms.

11. The process 01' claim 10, wherein the reaction is carried out at a temperature of 350 to 425 C.

12. The process of claim 10, wherein the polychlorohydrocarbon employed contains 2 carbon atoms.

. 18. The process of claim 10, wherein the polychlorohydrocarbon employed is symmetrical tetrachlorethane.

14, The process or claim 10, wherein the polychlorohydrocarbon employed is 1,2,2-trichlorethane.

15. The process of claim 10, wherein the polychlcrohydrocarbon employed is symmetrical tetrac'hlorethane and the reaction is carried out at a, temperature of 350 to 425 C.

- 16. The process of claim 10', wherein the polychlorohydrocsrbon employed is 1,2,2-trichlorethane and the reaction is carried out at 350 to CHARLES A. BORDNER.

summons crrsn ,The following references are of record in the tile 0! this patent:

Borsche et aL, Bericht der deut. Chem. GeselL," vol 48, pages 452-8 (1915).

V Busch et ai., IbicL, vol. 49, pages 1063-8 (1916).

Kelber, Ibid., vol. 50, makes 305-10 (1917). Vavon et al., "Comptes Rendus," vol. 206. pages 

1. A PROCESS FOR PRODUCING AN OLEFINIC COMPOUND COMPRISING REACTING HYDROGEN AT A TEMPERATURE OF 300 TO 500*C. IN THE PRESENCE OF A METALLIC CATALYST FROM THE GROUP CONSISTING OF COPPER AND IRON, WITH THE VAPORS OF A SATURATED POLYCHLOROHYDROCARBON HAVING FROM 2 TO 3 CARBON ATOMS AND AT LEAST ONE CHLORINE ATOM ON EACH OF TWO ADJACENT CARBON ATOMS. 